To find an estimate of calories needed for your body to maintain all metabolic activity in a day, simply take your body weight and multiply it by 10. The product will be your minimum amount of calories needed to maintain basal metabolism at that body weight. For example, a 175-lb. person will need 1,750 calories to maintain metabolic activity and stay at that weight. Apply your physical activity throughout the day to accommodate for additional calorie intake needed if your goal is to maintain current body weight.

If you choose to lose weight in terms of diet, consume less calories than required to meet your energy needs for the day. If you choose to gain weight, consume more calories than required to meet your energy needs for the day.Fat Intake

Fats should be 25 to 35 percent of your caloric intake. Fats yield 9 calories per gram. Eating fats is necessary for chemical reactions in the body such as absorbing fat-soluble vitamins and supplying energy for brain cells. Keep trans fatty acids and saturated fats at low intake, around 7 percent of total consumption.Carbohydrate Intake

Carbohydrates should be 50 to 60 percent of your caloric intake. Carbohydrates should be derived mainly from foods rich in complex carbs. Carbs yield 4 calories per gram.Protein Intake

Most people need 0.7 to 0.9 g per kilogram of body weight to meet the recommended intake for protein. Any more is either stored away in the body as fat or dispelled from the body. Maintain protein intake at 10 to 25 percent of your caloric intake. Proteins yield 4 calories per gram.